When a shotgun is fired, the pellet charge emerges from the muzzle as a single mass and remains so for a couple of feet, after which the pellets begin to disperse. This dispersion increases with the range of firing. The relationship between the size of pellet pattern and the range of firing is routinely employed in forensic science laboratories to estimate the range of firing. The method consists of firing test shots from different distances using the weapon of the crime and ammunition similar to that used in the crime and ascertaining the limits of the distance within which a pattern of the size of the evidence pattern can be obtained. This approximately defines the limits of the range of firing.